


Double Bind

by orphan_account



Category: Undertale (Video Game)
Genre: Frottage, M/M, Multiple Orgasms, Papyrus has stamina for days, Sexual Exhaustion, Sibling Incest
Language: English
Status: Completed
Published: 2015-12-06
Updated: 2015-12-06
Packaged: 2018-05-05 05:53:39
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,239
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/5363873
Author URL: https://archiveofourown.org/users/orphan_account/pseuds/orphan_account
Summary: <blockquote class="userstuff">
              <p>A little playful roughhousing leads to something... unexpected.</p>
            </blockquote>





	Double Bind

**Author's Note:**

> A fic loosely inspired by this little comic: http://likkrrr.tumblr.com/post/133037645006/i-am-gross-also-sans-with-sensitive-ribs-is
> 
> I hope you guys enjoy reading this as much as I enjoyed writing it. Haven’t had this much fun with a fic in a loooong time. :)

With a great  _‘thud’_  Sans hit the floor beneath the weight of his brother. His elbow scraped the carpet hard enough to give anyone with skin a serious road rash. Papyrus had just pounced upon him from the foot of the stairs with all the deadly determination of a hungry jaguar. After so much time spent chasing around someone who could teleport, one couldn’t blame him for his enthusiasm.

Sans was laughing.  _He couldn’t stop._  All attempts to fight Papyrus off were impeded as a result. The taller skeleton was clutching at his hoodie and all Sans could do was squirm and push at his hands.

“I have you now, Sans!” Papyrus cried triumphantly, though he sounded a little out of breath. “You have no hope of escape, so stop trying!”

In response Sans held tight to his own hoodie and tried to curl in on himself in the manner of an armadillo.

_“Sans!!”_

Papyrus did his best to thwart his brother’s actions, wrestling with him to try to get his hoodie off.

“If you don’t give me your clothes right now I’m… I…” Papyrus struggled to come up with a suitable threat. “I’ll just wash you with them!”

This only made Sans crack up even harder. It was a good thing monsters didn’t need to breathe. He’d probably be halfway to a blackout by now.

“Do you think I’m joking?!”

Sans shook his head ‘no’. He unfurled and attempting to kick and claw his way out from underneath the other monster. This only gave his brother an opening. Before he knew it his hoodie was half-way off his arms and he could no longer see. Alas, he was forced to relinquish the fight on that one.

“Ah-ha!” Papyrus shouted, tossing the pilfered sweatshirt aside to keep his hold secure.  _“Still_ not ready to declare defeat, brother!?”

 _“N-never,”_  Sans panted, feigning deadly seriousness.

His brother grasped at his shirt, long, thin fingers sliding roughly against his ribs. Sans jolted and let out a shocked, breathless cry. Figuring he’d found a weak point Papyrus went in for the kill with both hands. He attacked his ribs, rubbing between the gaps and jabbing roughly at his poor brother’s sides as he squirmed and fought with renewed urgency.

“S-stop!  _Please!_  P-Papyrus…!”

Maybe his protests would have been heeded if it weren’t for the fact he was still laughing. He twisted to push at his assailant and clutch at his arms. He was almost screaming between heady gasps.

“Please stop!” he laughed.  _“S-stop!”_

The sadistic grin on his brother’s face, however, was answer enough to his pleas.

“I don’t think I will, brother. Consider this your punishment!”

Sans didn’t know when his eye turned neon blue, but he could feel it burning now. His magic was rushing hot through his bones in response to all this over-stimulation. He jolted again upon feeling those teasing fingers glide between the gaps near the base of his ribcage, eyes wide with a sudden, horrible realization. He turned over onto his stomach again, pointed fingertips scraping the carpet. A particularly rough touch had him choking on a cry that threatened to become a moan. He wasn’t laughing anymore.

“Papyrus, seriously, knock it off.” He said, trying to keep the tone light in spite of everything.

“Why?” Papyrus immediately stopped, brow furrowed with concern. “Did I hurt you!?”

“No, you…” he saw no reason to dance around the subject with his own brother. “You’re giving me a boner.”

“A  _what?_  Wait… is this another one of your stupid jokes, Sans?”

Clearly he wasn’t getting the message. Sans grabbed Papyrus hand and shoved it between his legs to  _show_  rather than  _tell._ This forced the taller skeleton to hunch over him. He expected his brother to jerk his hand away with disgust. To his absolute astonishment, however, Papyrus slid his hand further and  _squeezed_ instead.

Sans pressed his face into the floor with a startled, “H-hah! Wh--”

“Wowie, Sans!” Papyrus sounded almost impressed. “I didn’t know you could do this, too!”

Sans was too stunned to react. His legs parted automatically as his brother kept squeezing and touching, getting a feel for his cock through the fabric of his shorts. Sans' cheeks were burning. He hid his face in his arm and shuddered. Papyrus had always been a little naïve, but Sans could hardly believe this was actually happening. Maybe it made sense. This reaction clearly wasn’t an involuntary one for Papyrus. No.  _He_  actually had powers he could  _control._

It would have been easy for Sans to put a stop to this indecent exploration if he really wanted to. No matter what, overstepping boundaries wasn’t something either of them would do to one another. He just didn’t  _want_ him to stop. He couldn’t remember the last time someone touched him like this. Couldn’t remember the last time it didn’t feel  _wrong._

“Yours is so thick.” Papyrus ruminated aloud.

Those words sent a bolt of lust down Sans’ spine. He muffled a loud moan against his arm, his hips twitching of their own accord. It took every ounce of his willpower to keep from outright trying to fuck his brother’s hand.

“Uh… Y-yeah, it sure is, bro,” he breathed, somehow able to manage a sardonic edge to his tone.

It was at this point that Papyrus’ innocent curiosity began to shift. They both knew what was happening here. He could have stopped if he wanted to. His touch faltered. Uncertainty was rife in the way his fingers twitched. Then, finally, he gripped Sans’ cock as best he could through the fabric and stroked downwards. Sans’ breath caught and he twisted, spreading his legs wider while keeping his face averted.

“Is this bad?” Papyrus asked, pausing.

“No, that…” Sans whimpered at the loss of friction, “It felt really good.”

The motion was resumed immediately. A firm squeeze to the head of his cock had Sans jerking his hips into it. This time he couldn’t control the reaction even if he wanted to. He fell back, sighing harshly and shivering as Papyrus rubbed soothing circles upon his frenulum. He dared to peer over his arm to see his brother’s expression. He couldn't remember the last time he’d seen him so  _enthralled._  There was a touch of worry to his gaze, too, or perhaps it was just intense concentration.

“Your eye is glowing,” he pointed out.

Sans gave a tiny, halfhearted chuckle, hiding his face again. “It does that all the time, Papyrus.”

“Well. Yes. But it doesn’t  _keep_  doing it.”

“Hn—don’t worry about it, bro.”

“Is it because of this?”

He squeezed his brother’s cock and gave it a little tug. Sans’ breath caught in his throat and his heel skidded up the carpet.

“If I say yes--” he hissed through his teeth, trying to drag the frustration out of his voice with a hint of forced amusement, “Will ya stop talkin’ about it?”

There was a short silence as Papyrus leaned further over him, sliding a hand up his brother’s shirt as he toyed with him.  _His touch felt uncertain again._  It was enough to make Sans squirm, a stab of worry keeping him from complaining. He sent a look up at his brother, hoping beyond hope he wasn’t just  _now_  having second thoughts.  _Realizing just how wrong this was._

“…Sans,” Papyrus began, hesitating in a way that was very unlike him. “Can I… um…  Can I see it? Please?”

It took a second for Sans to realize what he was talking about. The silence was broken by a small, breathy chuckle of relief. It was next to never that Sans actually got to witness Papyrus being _shy_  about asking him for something. It was unbearably cute.

“Heh… only if you show me yours.” Sans responded with a sideways leer.

It was always difficult to tell when he was being serious. Nevertheless, Papyrus took his words to heart.

“I agree to your terms.”

He hooked his fingers beneath the waistband of Sans’ shorts and tugged. Sans arched his hips up a bit and averted his gaze, not bothering to watch as his erection sprang free. He already knew what it looked like. He didn’t need a reminder.

That’s what he told himself as he bit back a violent wave of shame. He could feel his brother’s gaze upon him. There was a short delay, which he realized was caused by Papyrus removing his gloves, as next he felt warm, bare bone encircling his dick. It twitched so hard he flinched, unable to help shooting his gaze down with some alarm.

Papyrus’ expression was no less rapt than before. Delicately he tipped Sans’ cock to the side to get a better look at it, inspecting it like a precious gemstone.

“It’s very pretty, Sans,” he said, sounding  _surprised_ as he tipped it the other way. “This is my favorite color blue. Even if blue isn't my favorite color...”

He gave it a stroke, observing the magic’s reaction to his touch; or so Sans assumed. He could only watch with a mixture of lust and subdued mortification as this happened. His fingertips dug hard into the carpet and his brow was furrowed. A great big drop of precum oozed from the tip on the upstroke and rolled down the side, collecting upon Papyrus’ fingers.

“Hey, uh…” Sans distracted him, “You gotta show me yours, remember?”

Papyrus looked up at him.

“Of course I haven't forgotten, brother!”

He let go and propped himself up on his arms over Sans, nearly kneeling between his legs. The smaller of the two glanced up with a spark of trepidation mixed with anticipation. Papyrus’ head was tilted down, eyes narrowed with concentration. Sans turned further onto his back and gripped his brother’s forearm near the elbow.

Papyrus used his free hand to pull his own shorts down, slowly so that his newly formed erection caught and tented the fabric for a moment. If Sans didn’t know any better he’d say he was _teasing_  him on purpose. He couldn’t take his eyes away, suddenly,  _voraciously_ eager for the sight about to befall him. It sprang free at last, hard as a rock and glowing  _orange_. Already it was dripping. Even as Sans stared a long string of pre-cum fell from the tip and  _almost landed upon his own._

His grip tightened and he shuddered, looking almost pained for a moment. His cock jumped.

“Oh, man… Papyrus…” Sans breathed.

The taller skeleton shot a look down at him.

“Is something wrong?”

“Not wrong,” he responded, “It’s  _perfect._  Come closer.”

He grabbed the other’s shirt and dragged him down into a near embrace. He clutched at his upper arms as he pulled their hips together with his legs, shifting until their cocks slid flush against each other. He didn’t know why he did it,  _he just felt like he had to._

The sensation was like nothing else.

Their magic sparked together upon contact, arching like electricity. It crackled along his pelvis like an array of tiny thunderstorms. Static ecstasy danced up his spine to drive every last coherent thought from his head. Judging by that sharp gasp and the way his brother shook against him Papyrus’ experience was no different.

“Ah--! Sans…!”

Neither of them were prepared for that. Papyrus was pressing closer, his body tensing every time Sans ground against him, but he was obviously clueless on how to reciprocate.

“Move your hips, Papyrus…” Sans instructed, tremulous and panting, “Like me.”

And so he tried, eager to please as ever. His first movements were stuttering and uncertain, but satisfactory nonetheless. He fell to one of his elbows to brace himself upon the carpet as he grew more vigorous. Their chests pressed together, ribs fitting against one another like puzzle pieces.  Sans embraced him as best he could, gripping his shirt.

“T-that’s it, bro.” He breathed against the other skeleton’s clavicle.

He set a rhythm that Papyrus quickly fell into. Soon he barely had to move at all, which was exactly what he wanted. He hooked his legs over his brother’s hips and let him fuck him vigorously into the carpet. The pace he set was surprisingly overwhelming to begin with. Sans curled his fingers against his brother’s back, tips catching on the dips of his ribcage as he found a hold. He panted, vision wavering and expression slack with ecstasy.

“It… feels so  _good…_  Sans…” Papyrus panted, speech broken with the harshness of his movements.

Those words were breathed directly into Sans' ear, or would have been if he had one. His only response was a moan as he clutched at his brother harder. Shit,  _he wasn't going to last long at the rate this was going._  He wondered just how long Papyrus would keep this up. Lacking refractory periods, monsters didn’t really ever  _have_  to stop; not until they got _tired,_  which was a problem because  _Papyrus never got tired._

The thought was a fleeting one. It was difficult to worry when your entire being was wracked with overwhelming ecstasy. Wherever their bones touched energy crackled. The very fabric of their souls was meeting and reacting-- responding to the intensity of their union with increasing fury.

Sans tensed up about a couple minutes in. He bucked his hips with sudden urgency as his orgasm surged upon him without warning. He panted harsh and uneven, pulling himself close with his legs and gripping his brother's shirt in a death grip as he began to throb. With eyes squeezed shut he felt his own cum splatter against his spine and lower ribs in several long, hot spurts.

Papyrus didn’t once pause. The electricity between them had amplified in response to his brother's release enough to send him tipping over the edge as well.

“Sans…!” he panted, voice weak with alarm dipped in raw pleasure. 

He abruptly halted his movements. His whole body was _shaking._

“It’s alright, Papyrus… Just let it happen.”

Sans barely managed to speak through his post-orgasmic haze. Immediately Papyrus resumed his movements, giving several swift thrusts before abruptly stopping again. Sans turned his gaze down to watch with heavy-lidded eyes as his brother’s cock pulsed against his own. Papyrus' hips twitched. He cried out breathlessly, too shocked and overwhelmed by the sensations to stop himself. Several volleys of luminescent cum joined what was already soiling Sans' shirt and spine.

“Oh, Sans…” Papyrus breathed, panting raggedly.

He stroked his brother’s cheek, moving down to nuzzle against his face in what was the best he could give in terms of a kiss. He said his name again softly like a forbidden mantra. Sans returned the gesture, holding on to him as he trailed lazy kisses upon his teeth and jawline. He really did love him more than anything in the world. Right now his soul was filled to bursting with the emotion. He felt no shame in this moment, no fear; only the deepest, rawest affection. 

"I love you so much..." the words left his mouth unbidden.

"I love you too, Sans," Papyrus responded upon an exhale.

Magic still crackled hot between them. Neither of their erections were going away anytime soon if they stayed like this. After only a moment to catch his breath, Papyrus started up again. Sans had expected no less. He did his best to reciprocate, but he was already worn out. It took them both twice as long to reach orgasm.

With Sans dazed and devoid of the will to protest, Papyrus decided to go for a  _third_ round after that, followed by a fourth and then a  _fifth._

At that point Sans was beyond the ability to even hold on, anymore. His brother decided to take matters into his own hands. He slid his palms beneath Sans’ hips to get him to arch up into him as he thrusted. The energy was so thick in the air between them that Sans could feel it prickling at every inch of his body.

By the time the sixth rolled around Sans finally found it in himself to weakly push at Papyrus' chest.

“P-please, I can’t… anymore…”

To his amazement, Papyrus responded by grasping his wrists and pinning them down upon the carpet. The moment Sans saw that glazed, intoxicated expression on his brother's face he knew he wasn’t going to be getting out of this anytime soon. His previously pure, innocent brother was drunk on these new, mind-blowing sensations. He could always use his magic to free himself, but there was no way in hell he’d use those powers against Papyrus. Not even if his own life were at stake.

He writhed beneath the heated friction as it continued, staring pathetically up at his brother.

“C-c’mon, Papyrus,” he pleaded, but even to himself he sounded half-hearted.

_“But doesn’t it feel good, brother?”_

His voice sounded drugged, low and husky. The question Sans couldn’t lie to.

“Yes…” he nearly whispered in defeat.

In that position he took it, open and willing as he was brought yet again to an orgasm his body could barely handle. After that Papyrus still didn't stop. He switched to leaning on Sans again while propping his hips up, desperately grinding into him. This went on for what had to have been hours, both of them riding through orgasm after orgasm together until Sans lost count and eventually,  _consciousness._

-

He didn’t know exactly when it’d happened or how long he’d been out cold. All Sans knew was one moment he was being fucked senseless and the next he was waking up upon the livingroom couch. He forced himself to sit up even though he felt like he'd somehow gained a thousand pounds.

He couldn’t help but wonder if all that had actually happened or if he’d simply dreamt it.

A sharp look in the direction of where his brother had had him pinned was answer enough. A great big wet spot darkened the carpet. Propped up against the wall nearby was a steam cleaner.  _Of course Papyrus’ first instinct would be to clean up their mess._  He looked down at himself to confirm the fact his shirt had been pilfered as well. Sans rubbed his hand over his face with a tired chuckle. 

It all felt so unreal even staring at the evidence.

“Sans!” Papyrus’ voice startled him.

He looked up to see his brother rushing from the kitchen toward him, his expression rife with some mix of irritation and concern.

“I was beginning to think you’d never wake up! Don’t scare me like that!”

Sans merely closed his eyes and fell back onto the couch.

“Sans! I’m being serious! I thought you…” he hesitated. “I thought I’d… broken you.”

“Relax.” Sans peeked one eye open at him, “You could never break me. These bones are made of solid titanium.” He tapped his fist against his ribcage for emphasis.

Papyrus squinted at him.

“Could you… uh, maybe do me a favor? Since you’re already up.” Sans refused to let the silence get awkward. “Get me a bottle of ketchup from the fridge? I’d do it myself, but I can’t feel my legs.”

With an exasperated sigh Papyrus rolled his eyes. “Yes, brother. But don’t think this means I’m going to wait on you all the time, lazybones!”

Only when he turned his back did Sans let a fraction of his true emotion show. Whatever had happened between them tonight… well, the longer they could go without talking about it the better.

**Author's Note:**

> As usual, thoughts? Comments? Let me have 'em. I'd love to hear what you thought of it.


End file.
